Apparatus for bonding a low density material to a plastic substrate

ABSTRACT

An apparatus for and a method of bonding low density or thin gauge polyurethane foams to polypropylene substrates, said apparatus including, a revolvable turntable for indexing the workpieces to various work stations, a conductive heating station to heat-liquify designated areas of the polypropylene substrate, and a compression station having compression platens to emboss the polyurethane foam onto the polypropylene substrate effectively fusing the fibers of the polyurethane foam with the heat-liquified areas of polypropylene. The method generally includes the steps of, engaging the surface of a precut polypropylene substrate with a heated member for a predetermined period of time to cause the polypropylene to heat-liquify at the points of contact forming a raised quantity of melted polypropylene, removing the heated member from contact with the polypropylene, placing a pre-cut sheet of polyurethane foam into contact with the melted polypropylene, applying pressure to the polyurethane foam so as to fuse the fibers thereof with the melted polypropylene, and permitting the fused polyurethane and polypropylene to cool effectively bonding them together.

This is a division, of application Ser. No. 07/206,709, filed 06/15/88,now U.S. Pat. No. 4,854,993, which is a division of Ser. No. 07/097,655filed 9/17/87 now U.S. Pat. No. 4,794,030.

BACKGROUND OF THE INVENTION

This invention relates to a method of and an apparatus for making acomposite laminated structure comprised particularly of a sheet ofpolyurethane foam or other material which is similarly low in densityand a polypropylene substrate or the like.

Thermoplastic plastics, particularly polypropylene, portray a variety offavorable characteristics and properties including that of being easilymolded and that of chemical inertness; and thus, such plastics are idealfor a plurality of applications. Such plastics are also comparitivelyinexpensive, and therefore particularly desirable for use in themanufacturing of articles of commerce adapted as disposable packages forfood and health and beauty aids. However, in certain packagingapplications, for instance where chemical compositions are involved, theitem or composition being packaged will not readily adhere to theplastic, as might be required, because of the properties of the plasticand/or the composition itself. An example of such a packagingapplication is where a polypropylene material is used to form adispensing container for a solid anti-perspirant/deodorant composition.

It is these packaging applications which require some means to ensurethat all compositions adhere to the polypropylene in the desired areas.The inventor herein has discovered that fixing a layer of polyurethanefoam to the polypropylene is the most inexpensive and perhaps only meansof accomplishing the above. When this concept is reduced to practice,all such solid compositions will readily adhere to the layer ofpolyurethane foam, and therefore will become fixed in relation to thepolypropylene. Without such a structure, the use of polypropylenematerials in the above mentioned packaging applications might not bepossible or feasible from the viewpoint of cost and benefit derivedtherefrom.

The problem arises, however, as to the proper mechanical technique toeffect the bonding of the polyurethane foam to the polypropylene.Techniques for laminating plastic resin materials are well known in theart, and include methods and apparatus by which the plastic resinmaterial, in its entirety, is heated and the covering material issubsequently rolled or compressed on the plastic resin material in itssoftened state.

Thus, U.S. Pat. No. 3,533,866 discloses a method which uses a flamelaminator to heat and tackify polyolefin fiber batts which areimmediately laminated to a layer of flexible polyurethane foam.Similarly, U.S. Pat. No. 3,318,744 discloses a method which utilizeselongated ribbon type flames issued from a plurality of orifices to heatthe surface of a polyurethane foam material which is held under tension(so as not to wrinkle). A reenforcement layer is then laminated to thepolyurethane foam with a reenforcement layer. The apparatus and methoddisclosed in these Patents, however, are dangerous, costly, requirestrict supervision. Moreover, such apparatus and methods are ineffectivewhere the polyurethane foam is of particularly low density or ofrelatively thin gauge.

U.S. Pat. Nos. 3,062,698 and 4,225,376 teach methods by which a coveringmaterial is heated to a temperature above the melting point of a foamthermoplastic resin, on which the covering material is immediatelypressed. The methods disclosed in these patents are ineffective becausethey heat and soften the entire material on which the foam is to bepressed, thus deforming the shape and critical dimensions of thematerial.

U.S. Pat. No. 4,356,012 teaches a method which uses a heated die with acentral relief groove to seal a hydrophobic filter material to a urinarybag made of polyvinyl chloride. This method is inapplicable for bondinga sheet of polyurethane foam to a polypropylene substrate because itcalls for the direct sealing of two materials together, the first ofwhich is a filter screen made of a material which is resistant to heat.

Although not shown specifically in the prior art, it should be notedthat the use of a glue or an epoxy to effect the desired bonding betweenthe foam and polypropylene substrate has been unsuccessful for tworeasons. First, the types of glues and epoxies which will adhere topolypropylene plastics are limited. Secondly, the surface area of thefoam susceptible to such bonding is minimal and therefore any bond whichmight be made is correspondingly weak. Further, gluing or epoxyingsmaller items can be tedious and expensive from the standpoint ofmanufacturing, requiring long periods of time for drying and completingthe bond.

The present invention is directed to an apparatus for and a method ofbonding particularly low density or thin gauge materials to substratesmade of polypropylene or the like to form a composite laminatedstructure in which the structure, characteristics and properties of thepolyurethane foam and the polypropylene substrate are not substantiallyaltered thereby.

The broad method of bonding thin layers of low density materials to apolypropylene substrate in accordance with the present invention can bevaried and altered for adaptation to a variety of manufacturingapplications. By employing the apparatus and method herein, any materialwhich has heretofore resisted bonding to polypropylene or the like, orrequires expensive techniques to effect such bonding, can be readily andinexpensively bonded thereto.

The composite laminated structure obtained by the method and apparatusof the present invention can be used in the construction of manyproducts, and in particular, to products requiring polyurethane foam asa protective cushion or to anchor a composition to a relatively strongpolypropylene casing or container which can be adapted, prior to bondingthe polyurethane foam thereto, for snap-fit assembly or any other meansof fastening.

SUMMARY OF THE INVENTION

The present invention broadly contemplates an apparatus for bonding to apolypropylene substrate low density or thin gauge materials which haveheretofore resisted such bonding by conventional methods, said apparatuscomprising, an indexing turntable having, a workpiece holder to receive,for example, a polypropylene substrate and a sheet of polyurethane foam,a conductive heating station, a compression station, means to rotatesaid workpiece holder into alignment with a respective work station, andmeans to regulate the time in which the workpiece holder dwells at agiven work station. The conductive heating station is situatedinteriorly adjacent to the perimeter of the turntable, and includes, apneumatically controlled descendible and retractable plate member havingat least one welding iron thereon, means for heating said plate memberand at least one welding iron to a predetermined temperature, means forsynchronizing the descending and retracting movement of the plate memberwith the rotary movement of the turntable, and an exhaust duct to drawoff any harmful fumes which might be generated by contacting the weldingiron to the plastic substrate. The compression station is similarlysituated interiorly adjacent to the perimeter of the turntable at apredetermined angular distance from the conductive heating station, andincludes, a pneumatically controlled descendible and retractablecompression platen having at least one individual platen to emboss thelow density material into the plastic substrate at the point at whichthe welding iron softened and raised the plastic, and means forsynchronizing the descending and retracting movement of the compressionplaten with the rotary movement of the indexing table.

Additionally, the apparatus as above described wherein a storage hopperand/or a robotic arm are operatively associated with the turntable forautomated placement of the plastic substrate in the workpiece holder.Further, safety shields having emergency shut-off switches which areactivated when the shields are contacted are provided at the foamplacement station and at the substrate placement station providing ahopper or robotic system are not utilized.

In addition, the present invention particularly contemplates a methodwhereby the apparatus as above described is implemented, said methodcomprising the steps of, engaging the surface of a plastic substratewith at least one welding iron for a predetermined period of timesufficient to cause the contacted surface to soften only at the pointsof contact, removing said at least one welding iron, placing a sheet oflow density or thin gauge material on the surface of the plasticsubstrate having the softened areas thereon, embossing the low densitymaterial onto the plastic substrate at the softened areas thereof tofuse the low density material into the softened areas of the substrate,and allowing the fused low density material and plastic substrate tocool, effectively bonding the materials to form a composite laminatedstructure.

Accordingly, it is an object of the present invention to provide anapparatus for manufacturing a composite laminated structure consistingof a material which is of particularly low density or thin gauge and apolypropylene material or the like.

It is another object of the present invention to provide a specificmethod by which the above described apparatus or any other suitableapparatus can be implemented to effectively bond materials of lowdensity or thin gauge to a polypropylene substrate.

It is another object of the present invention to provide an apparatusfor and a method of bonding polyurethane foam to a polypropylenesubstrate without rendering useless the molded structure of thepolypropylene substrate or destroying the desirable characteristics ofthe polyurethane foam.

It is another object of the present invention to provide an apparatusfor and a method of bonding polyurethane foam to a polypropylenesubstrate which is substantially automated requiring only a minimaldegree of supervision and participation by the operator.

It is yet another object of the present invention to provide anapparatus for and a method of bonding a material of low density or thingauge to a plastic substrate wherein the structure and operation of theapparatus and the steps of the method are easily controlled and variedas may be required for particular applications and for the particularmaterials being bonded into a composite laminated structure.

These and other objects will become apparent, as will a betterunderstanding of the concepts underlying the present invention byreference to the detailed description which follows below and is to bestudied in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an indexing turntable and bondingapparatus including two workpiece holders, a conductive heating stationand a compression station, all in accordance with the present invention.

FIG. 2 is a top plan view of the indexing turntable and bondingapparatus shown in FIG. 1, wherein the indexing turntable has beenrotated.

FIG. 3 is a front elevational view of the indexing turntable and bondingapparatus shown in FIG. 1, wherein the indexing turntable has beenrotated.

FIG. 4 is a left side view of the indexing turntable and bondingapparatus shown in FIG. 1, wherein the indexing turntable has beenrotated.

FIG. 5 is a right side view of the indexing turntable and bondingapparatus shown in FIG. 1, wherein the indexing turntable has beenrotated.

FIG. 6 is a front elevational view of the conductive heating assemblyshown at the heating station of the indexing turntable and bondingapparatus in FIG. 1.

FIG. 7 is a front elevational view of the compression platen assemblyshown at the compression station of the indexing turntable and bondingapparatus in FIG. 1.

FIG. 8a is a diagrammatical depiction of the pneumatic system whichoperates the indexing turntable and the conductive heating assembly andcompression platen assembly shown in FIGS. 6 and 7, respectively.

FIG. 8b is a flow chart illustrating the sequence in which the elementsof the apparatus of the present invention are activated.

FIG. 9a is a schematic diagram of the electrical system which operatesthe indexing turntable and bonding apparatus shown in FIG. 1.

FIG. 9b is a schematic diagram of the electrical system which operatesthe heating unit within the conductive heating assembly shown in FIG. 6.

FIG. 10 is a bottom plan view of the conductive heating assembly shownin FIG. 6, illustrating in particular the heating elements thereof.

FIG. 10a is an enlarged broken away side view of an individual heatingelement, illustrating in particular the shape thereof.

FIG. 11 is a bottom view of the compression platen assembly shown inFIG. 7, illustrating in particular the compression platens thereof.

FIG. 11a is an enlarged broken away side view of an individualcompression platen.

FIG. 12a is a broken away cross-sectional side view of an individualheating element and polypropylene substrate before the heating elementcontacts the substrate at the conductive heating station on the indexingturntable and bonding apparatus of FIG. 1.

FIG. 12b is a broken away cross-sectional side view of the individualheating element and polypropylene substrate shown in FIG. 12a where theindividual heating element begins its contact with the substrate.

FIG. 12c is a broken away cross-sectional side view of the individualheating element and polypropylene substrate shown in FIG. 12a during thedwell period where the individual heating element is at a predetermineddepth within the polypropylene substrate, illustating in particular theformation of a raised quantity of softened polypropylene about theindividual heating element.

FIG. 12d is a broken away cross-sectional side view of the individualheating element and polypropylene substrate shown in FIG. 12a showingthe individual heating element removed from the polypropylene substrateleaving a depression of predetermined depth and most importantly araised quantity of softened polypropylene as formed about the individualheating element during the dwell period.

FIG. 13a is a broken away cross-sectional side view of an individualcompression platen and the polypropylene substrate as prepared at theconductive heating station (FIGS. 12a-12d) with a precut polyurethanefoam sheet placed on top of the raised and softened polypropylene.

FIG. 13b is a broken away cross-sectional side view of the individualcompression platen, polypropylene substrate after treatment at theconductive heating station and the precut polyurethane foam sheet, allshown in FIG. 13a, wherein the individual compression platen begins toapply pressure to the polyurethane foam sheet in the area of the raisedand softened polypropylene.

FIG. 13c is a broken away cross-sectional side view of the individualcompression platen, polypropylene substrate and polyurethane foam sheet,all shown in FIG. 13a, wherein the individual compression platen hasfully compressed the polyurethane foam and polypropylene substrate,effectively flattening the raised and softened polypropylene so as tobond the polyurethane foam to the polypropylene substrate.

FIG. 13d is a broken away cross-sectional side view of the individualcompression platen, polypropylene substrate and polyurethane foam sheet,all shown in FIG. 13a, wherein the individual compression platen isshown in its retracted position and the polyurethane foam is bonded tothe polypropylene substrate forming a composite laminated structure.

FIG. 14 is a perspective view of a composite laminated structure made inaccordance with the apparatus and method of the present invention, asillustrated in the preceding Figures.

FIG. 15 is a top plan view of a polypropylene substrate, wherein themolded structure thereof is adapted for snap-fit engagement with otherpolypropylene parts to form a container.

FIG. 15a is an enlarged cross-sectional side view of the polypropylenesubstrate shown in FIG. 15 as taken on line 15a--15a thereof.

FIG. 16 is a top plan view of the polypropylene substrate shown in FIG.15 after heat treatment of the same in accordance with the techniqueillustrated in FIGS. 12a-12d, illustrating in particular the softenedand raised areas of polypropylene.

FIG. 16a is an enlarged cross-sectional side view of the heat treatedpolypropylene substrate shown in FIG. 16 as taken on line 16a--16athereof.

FIG. 16b is an enlarged cross-sectional side view of the polypropylenesubstrate shown in FIG. 16 taken on line 16b--16b thereof.

FIG. 17 is an exploded perspective view of the polypropylene substratehaving eight circular beads of softened and raised polypropylene as aresult of treatment at the conductive heating station and a precut sheetof polyurethane foam as it is to be placed on the polypropylenesubstrate.

FIG. 18 is a top plan view of the composite laminated structureresulting from compressing the polyurethane foam, raised and softenedbeads and the polypropylene substrate shown in FIG. 17 in accordancewith the technique illustrated in FIGS. 13a-13d.

FIG. 18a is an enlarged cross-sectional side view of the compositelaminated structure shown in FIG. 18 taken on line 18a--18a thereof.

FIG. 18b is an enlarged cross-sectional side view of the compositelaminated structure shown in FIG. 18 taken on line 18b--18b thereof.

FIG. 18c is an enlarged partial cross-section of the composite laminatedstructure shown in FIG. 18a, illustrating the fusing of the polyurethanefoam fibers to the flattened bead of polypropylene.

DESCRIPTION OF THE INVENTION

Referring to the drawings, FIGS. 1-5 show a sealing apparatus generallydesignated as 10 and including, a base 11, an indexing turntable 12having on its upper platform surface 13 workpiece holders 14a and 14b, aconductive heating assembly 15, and a compression platen assembly 16.The structural details of the heating assembly 15 and the compressionplaten assembly 16 are shown in FIGS. 6-7 and 10-11.

The indexing turntable 12 of the sealing apparatus 10 is rotatablyconnected at its center to the base 11 by means of a rotatable shaft 17,which transmits the rotational energy of a pneumatically controlled airmotor (not shown) to the turntable 12. Operatively associated with thepneumatically controlled air motor are a limit switch and a time relaywhich together control the movement of turntable 12. The rotation ofturntable 12 is synchronized with the operation of conductive heatingassembly 15 and compression platen assembly 16 by means of proximityswitches 18a and 18b. Proximity switches 18a and 18b, best shown inFIGS. 1 and 2, include conventional sensing devices to detect the metalnibs 19a and 19b located on the peripheral edge of turntable 12. Whenthe metal nibs 19a and 19b are detected, a signal is transmitted to theconductive heating assembly 15 or compression platen assembly 16 tocause the heads thereof to descend for a predetermined period of time,that is, a dwell period. Simultaneously, the time set on the time relayexpires and the limit switch stops rotation of the table. It isimperative to note the location of the workpiece holders 14 in relationto metal nibs 19 since it is this arrangement which dictates thedescending movement of the heads of the conductive heating assembly 15or compression platen assembly 16 when the table 12 is stopped and theworkpiece holders 14 are thereunder.

The workpiece holders 14 can vary in size and shape depending upon thesize, shape and type of materials which are to be held therein forbonding. In the embodiment shown herein, the workpiece holders 14a and14b are each capable of securing two oval shaped workpieces such asthose illustrated in FIGS. 14-18. As shown in FIGS. 1 and 2, workpieceholders 14 include base means 20 having oval shaped depressions therein,a cover 22 having oval shaped openings for alignment with said ovalshaped depressions in said base means when the cover 22 is closed andhinge means 24 connecting the cover 22 to the base means 20.

In the illustrated embodiment, workpiece holder 14a is diametricallyopposed to workpiece holder 14b, however, workpiece holders 14 can besituated in any suitable arrangement or additional workpiece holders canbe fixed to the upper surface 13 of the turntable platform as long asmetal nibs 19 are installed in the correct locations so as to properlyindex the workpiece holders beneath the conductive heating assembly 15or the compression platen assembly 16. Of course, the number andarrangement of the workpiece holders will depend upon the size and typeof workpiece and the dwell period and indexing period.

The conductive heating assembly 15 of the present invention includes adescendible and retractable rod member 25 and cylinder 26 which coact ina piston-type arrangement. Air lines 27a and 27b introduce air into thecylinder 26 as the fluid medium by which a slide-valve arrangement inthe cylinder 26 is actuated to forceably lower and retract rod member25. The pneumatic system of which air lines 27a and 27b are integralparts is shown in FIG. 8a and will be discussed below.

A first plate member 28 is fixed to rod member 25 at the lower endthereof for movement therewith. A second plate member 29 is fixed to thefirst plate member 28 by any suitable fastening means so as to provide agap between first plate member 28 and second plate member 29. A heatconduit member 30 heats second plate member 29 to a predeterminedtemperature which can be precisely maintained by the use of athermocouple which continuously sends a signal to a thermoswitch or thelike. A schematic diagram of the heating elements which heats heatconduit member 30 is shown in FIG. 9b. In turn, the second plate member29 conductively transmits the heat to a plurality of welding irons orcontact heads 31 which are fastened thereto or made integral therewith.FIG. 10 shows a bottom view of second plate member 29 with welding irons31 fixed thereto in a pattern specifically adapted for bonding theworkpieces shown in FIGS. 14-18. It should be noted that the gap betweenfirst plate member 28 and second plate member 29 is provided preventfirst plate member 28 and rod member 25 from becoming heated.

It is particularly noted that welding irons 31 have tapered points 31a,as clearly shown in FIG. 10a. This configuration is particularlyimportant in preparing a plastic substrate for bonding with apolyurethane foam since it is the means by which the softened plasticmaterial will be raised so as to form a circular bead of molten plasticabout the contact head 31, which bead remains after the contact head 31retracts. The advantage conferred by this tapered point 31a will becomemore apparent from the description of the melting technique whichfollows below.

It is to be further noted that the welding irons are made of aluminumsince materials such as brass retain the residue of the plastic aftercontact therewith, and therefore the contact heads 31 have to be cleanedeven after a short term of usage. The use of materials such as brassalso inhibit the formation of the circular bead of softened plasticmaterial. Aluminum contact heads, however, provide for the efficientmelting of the plastic material with minimal residual deposits, thusforming full and clean circular softened areas.

As with any metal material used to melt plastics such as polypropylene,harmful fumes and vapors are emitted, thus an exhaust duct 32 isprovided to draw off any such harmful fumes or vapors.

FIG. 7 shows the compression platen assembly 16 which also operates onthe basis of a piston-type arrangement.

Thus, air hoses 33a and 33b are part of the pneumatic system depicted inFIG. 8a which effects the descendible and retractible movement ofcompression rod member 34 which is housed within the compressioncylinder 35. Fixed to the lower end of compression rod member 34 iscompression plate member 36 which includes a series of individualcompression platens 37, the pattern of which matches the pattern of thewelding irons 31, as can be seen by comparing FIG. 10 and FIG. 11. Asshown in FIGS. 11 and 11a, the individual compression platens 37 are ofa diameter which is greater than the diameter of the tapered points 31aof welding irons 31 to ensure that the entire circular bead of softenedplastic formed by heat treatment of the plastic substrate is embossed bythe individual compression platen 37. The individual compression platens37 can be formed from any suitable material such as aluminum or a highdensity rubber material.

The various elements of the bonding apparatus 10 are activated by meansof the switches mounted on the front of base 11, wherein power switch 38opens the AC power source, heat switch 39 activates the heating element30 to conductively transfer heat to the welding irons 31, turntableswitch 40 commences rotation of the turntable 12, sealing switch 41activates the portion of the pneumatic system which controls conductiveheating assembly 15, compression switch 42 activates the portion of thepneumatic system which controls compression platen assembly 16, andemergency switch 43a terminates operation of the bonding apparatus 10 inthe case of an emergency by cutting off the power thereto. Emergencyswitches 43b and 43c are respectively provided on the top and sidesurfaces of base 11 for the same purpose as emergency switch 43a.

Once the proximity switches and time relays have been set for thedesired application, bonding apparatus 10 is easily operated by firstdepressing power switch 38 and then turning heat switch 39 to heatwelding irons 31. The temperature of second plate member 29 and weldingirons 31 can be indicated on a digital or analog thermometer which is inline with the thermocouple and once the predetermined temperature hasbeen reached the remaining devices of bonding apparatus 10 can beactivated by opening the aforementioned switches. It should be notedthat the devices of bonding apparatus 10 are capable of independentoperation so that the various phases of operation can be explored andexamined on an experimental basis.

Of course, the descending and retracting movement of the welding irons31 and the compression platens 37 must be coordinated with the rotationof indexing turntable 12 in accordance with the desired bondingapplication. This coordination is accomplished by operativelyassociating the pneumatic system schematically illustrated in FIG. 8awith the electrical system schematically illustrated in FIG. 9. The flowchart in FIG. 8b summarizes the coordination of the various elements ofthe apparatus 10.

Thus, reference to FIG. 9a shows a 115 V power source which is protectedby a three ampere fuse F1. This power is supplied to the coils on relaysR1 and R3 by closing power switch 38. Turntable switch 40 is then closedto commence rotation of the turntable 12 and the cycle of the apparatus.It should be noted that emergency switch 43 is normally closed to permitrelay R3 to be energized. Lights LT1, LT2 and LT3 indicate when therespective elements of the apparatus 10 are receiving power.

A cam member (not shown) on the turntable 12 then activates limit switchLS1 which energizes timer relay coil TR1 for a predetermined period oftime permitting the coil on relay R2 to be energized. As the contacts ofrelay R2 open the air to the table air valve V1 is interrupted to stopthe rotation of the turntable 12.

Once the predetermined period of time is completed, time relay TR1 opensand causes R2 to close, whereby power is reinstated to table air valveV1 to resume the rotation of the turntable 12.

Safety proximity switches 18c and 18d are provided within conductiveheating assembly 15 and the compression platen assembly 16 to ensurethat the heads thereof are in their uppermost positions before rotationof the turntable 12 is resumed.

The operation of the conductive heating assembly 15 and the compressionplaten assembly 16 are integrated with the rotation of the turntable 12by activating, respectively, sealing switch 41 and compression switch42. As discussed above, the proximity switches 18a and 18b will readtheir respective metal nibs 19a and 19b to supply power to the timerrelay TR2 (for the conductive heating assembly 15) and the timer relayTR3 (for the compression platen assembly 16), for commencing themovement thereof.

Thus, after time relay TR2 is activated, power supplied to theconductive air valve V2 whereby the welding irons 31 will descend forcontact with the workpiece for the length of time (dwell time) set onthe timer relay TR2. The compression air valve V3 causes the compressionplatens 37 to descend in the same manner once time relay TR3 isactivated.

FIG. 9b shows the heat circuit which regulates the temperature of thewelding irons 31, in which the power source is 220 V single phasesupplied through a double pole switch SW4 and is indicated on light LT4.This power is fed to the three 220 V heating elements X, Y and Z. Thethermocouple, fixed on the second plate member 29, continuously sensesthe temperature of the second plate member 29 and the welding irons 31.When the temperature set on the heat control is reached, the power tothe heat control relay HCR is interrupted, opening the contacts HC1 tocut off the power to the heating elements X, Y and Z. The power to therelay HCR is cut off once the thermocouple senses a temperature belowthe desired temperature so that the contacts HC1 are again closed topermit power to the heating elements X, Y and Z. This process is inoperation continuously to maintain the welding irons 31 at the desiredtemperature.

Referring to the pneumatic diagram illustrated in FIG. 8a, the main airtravels into the adjustable air regulator in which the desired pressureis set and supplies air at the desired pressure to the turntable valveV1, the sealing valve V2 and the compression valve V3, all throughnormally closed ports. Prior to travelling to the valves, the air passesthrough an oiler in which a portion of the oil therein vaporizes and ismixed with the air to lubricate the cylinders of the valves.

Turntable valve V1 is a two-way electrical coil activated pneumaticvalve whereby the activation of the electrical coil C1 interrupts theair flow to turntable valve V1 to stop rotation of the turntable 12.

The air flowing to sealing valve V2, a four-way electrical coilactivated pnuematic valve, normally maintains the sealing head in itsuppermost position. Upon activation of the electrical coil C2, however,the air flow is reversed, permitting the air to flow into the top of thecylinder 26 to force the sealing head and welding irons 31 downward forcontact with the workpiece. This, of course, occurs when metal nib 19ais detected by proximity switch 18a.

Compression valve V3 operates in the same manner as sealing valve V2 todrive the compression platens 37 onto the workpiece.

A full cycle of operation of the apparatus 10 is shown in the flow chartin FIG. 8b. This flow chart shows the activation of the table limitswitch LS1., the stopping of the turntable 12, the descending anddetracting movement of both the sealing head and the compression head,and the rotation of the turntable between the sealing station and thecompression station.

To place the apparatus of the present invention into practice with themethod of the present invention, the basic steps of which are shown inFIG. 8b, two substrates of the type shown in FIG. 15 and generallydesignated as 50 are placed into workpiece holder 14a at loading stationA. These substrates are made from any type of thermoplastic plastic suchas polypropylene, and placement of the same into the workpiece holder14a can be accomplished manually by an operator located at loadingstation A or by means of an automatic hopper system in conjunction witha robotic transfer assembly, or any other suitable means. Once thesubstrates 50 are in position within the oval-shaped depressions 21a ofthe workpiece holder 14a the cover 22a is to be closed to secure theplastic substrate or workpiece 50 about the perimeter thereof and exposethe upper surface of workpiece 50 through oval-shaped openings 23a.

The workpiece holder 14a is then rotated towards the conductive heatingstation as the turntable 12 revolves. Once the workpiece holder 14a isaligned beneath the conductive heating assembly 15 the limit switch LS1stops the turntable 12 and metal nib 19a, located on the periphery ofturntable 12, will be in alignment with proximity switch 18a, the sensorof which will read the metal of metal nib 19a and cause the head ofconductive heating assembly 15 to descend. This is accomplished by meansof 80 PSI of air being introduced into cylinder 26 to forceably effectthe descent of the welding irons 31 which have been heated by heattransfer member 30.

It has been found that the air pressure utilized to effect thedescendible and retractible movement of welding irons 31 or compressionplatens 37 is not particularly critical. However, it has also been foundthat welding irons 31 should be heated to a temperature of approximately650° Farenheit when used in association with plastics such aspolypropylene, especially where the dwell period is in the order of 2.5seconds and the polypropylene substrate to be contacted is relativelythin, perhaps in the order of 0.050 gauge. The thickness of the plasticsubstrate, the depth to which the welding irons 31 will melt into thesubstrate and the time of the dwell period must all be considered andcoordinated when determining the temperature of the welding irons 31 andthe dwell period.

Referring specifically to FIGS. 12a-12c, the descending movement of asingle welding iron 31 is shown. Thus, FIG. 12b shows the tapered point31a of welding iron 31 as it contacts the polypropylene workpiece 50.The manner in which the polypropylene is softened and raised, shown asat bead 51, should be particularly noted. As the welding iron 31descends to its maximum depth within polypropylene substrate 50, shownin FIG. 12c, this softened bead 51 continues to flow upwardly and "roll"outwardly from the tapered point 31a of welding iron 31. The taperedconfiguration of the welding iron 31 enhances this "rolling" actionpartially by means of the angle surface and partially because of thehigh concentration of heat exhibited at the tapered point 31a.

Once the welding iron 31 has reached its maximum depth withinpolypropylene substrate 50, air is introduced into cylinder 26 to effectthe retracting movement of the welding irons 31 and the remainder of themoving elements of the heating assembly 15, as shown in FIG. 12d.

FIG. 12d further shows the depression 52 formed by the tapered point 31aof welding iron 31 as well as the raised and softened area ofpolypropylene or bead 51. FIG. 16 shows a top plan view of thepolypropylene workpiece 50 immediately following treatment of the sameat the conductive heating assembly 15. Thus, an oval-shaped pattern ofeight circular depressions 52 and the raised circular beads 51 ofsoftened polypropylene material. FIGS. 16a and 16b show cross-sectionsof the polypropylene substrate shown in FIG. 16, in which selectdepressions 52 and beads 51 are shown.

It is to be particularly noted that the structure and elements ofpolypropylene substrate 50 have not been damaged or affected in any wayfollowing treatment at the conductive heating station.

The welding irons 31, as well as first plate member 28, second platemember 29 and rod member 25, will retract to their original positions inrelation to the indexing turntable 12. At this time, the safetyproximity switch 18c within conductive heating assembly 15 will beactivated to permit rotation of the turntable 12 to be resumed once thetime relay times out. This switch is activated when the welding irons 31and other elements of the conductive heating assembly 15 are in theiruppermost positions to ensure that rotation of turntable 12 does notcommence prior to the full retraction of these elements.

The workpiece holder 14a is then indexed to work station B where anoperator manually places a pre-cut piece of material, in this case anoval-shaped piece of polyurethane foam 53 onto the polypropylenesubstrate 50 with the raised and softened areas. An example of the typeof polyurethane foam contemplated for use with the present invention isone having a density of approximately thirty pores per inch and is0.125" in gauge. One skilled in the art will recognize, however, thatthe material to be bonded to the plastic substrate 50 by the presentinvention can be covering material of any type.

FIG. 17 shows the polyurethane foam 53 as it is placed onto the heattreated polypropylene substrate 50. It should be noted that it ispossible to formulate an automated system for placing the foam 53 ontothe substrate 50, perhaps a shuttling system at the compression stationimmediately prior to compression. Such a shuttling system would includea member similar to the cover 22 of the workpiece holder 14 on which thefoam could be deposited. That member would then slide into position overthe treated polypropylene prior to compression.

The indexing time, that is the time from which the polypropyleneworkpiece 50 is treated at the conductive heating asembly 15 to the timethat the compression platens 37 compress the polyurethane foam 53, is ofparticular concern in the present invention. If this indexing time iselongated the raised and softened area 51 of the polypropylene workpiece50 will solidify or partially solidify thus preventing an effective bondfrom being made between the polyurethane foam 53 and the polypropyleneworkpiece 50. The ambient temperature during operation plays the mostimportant role in determining the indexing time. For instance, anindexing time of 2.8 seconds prevents the hardening of the bead 51before compression when the ambient temperature is approximately 75°Farenheit. The inventor herein has discovered, however, that if theindexing time can be limited within the range of 1.9-2.4 seconds, thenthe effect of the ambient temperature can be disregarded. This discoveryholds true at least with respect to thermoplastic plastics such aspolypropylene.

One skilled in the art will readily recognize that a shuttling systemsuch as the one described above would permit the compression assembly 16to be closer to the conductive heating assembly 15, effectively reducingthe indexing time.

Once the workpiece holder 14a is in alignment with compression platemember 36, air at a pressure of 80 PSI is introduced into thecompression cylinder 35 to actuate the slide valve within cylinder 35 todescend the compression rod member 34, compression plate member 36 andcompression platens 37 as shown in FIGS. 13a-13c. As these Figuresillustrate, the individual compression platen 37 shown thereincompresses the polyurethane foam 53 into the raised and softened bead 51formed by the tapered point 31a of welding iron 31. At its lowest point,the compression platen 37 contacts the surface of the polyurethaneworkpiece 50, to flatten the raised and softened bead 51 which is nowfused with the polyurethane foam 53. Once the downward motion ofcompression platen 37 is completed, air is introduced to the oppositeside of the slide valve within cylinder 35 to retract the compressionplaten 37, compression plate member 36 and compression rod member 34, asshown in FIG. 13d. As with the conductive heating assembly 15, a safetyproximity switch within cylinder 35 permits the reactivation of theturntable 12 which indexes the workpiece holder 14a back to loadingstation A or any work station between the compression platen assembly 16and loading station A. During such rotation to loading station A theflattened bead 51 is permitted to cool effectively bonding thepolyurethane foam 53 to the polypropylene workpiece 50 through the poresof polyurethane foam 53. After the flattened bead 51 has sufficientlycooled, the finished product, a composite laminated structure 54, can beremoved from the workpiece holder 14a.

The product of the present invention consists of a composite laminatedstructure such as those shown in FIGS. 14, 18, 18a, 18b and 18c.Reference should also be made to FIG. 13d since it shows an enlargedportion of the composite laminated structure 54. The detail of thebonding between the laminate and the substrate can be seen clearly inFIG. 18c, an enlarged partial cross-section of the composite laminatedstructure 54.

Thus, the aforementioned Figures show a polypropylene substrate 50having a plurality of depressions 52 which include about their peripheryflattened rings or beads 51 of polypropylene. A sheet of polyurethanefoam 53 or the like is bonded to the polypropylene substrate 50 by meansof these flattened rings or beads 51. This is accomplished by the ringsor beads 51 fusing the polyurethane foam 53 to the polypropylenematerial through the fibers and pores of the polyurethane foam 53,effectively anchoring the polyurethane foam material within theflattened circular bead 51.

Specific reference to FIG. 18c reveals that the polyurethane foam will,in most instances, fill the depression 52 so that the loss ofpolyurethane foam cushion or adhering surface in the area of thedepression 52 and bead 51 is minimal. FIG. 18c further shows the mannerin which the fibers of the polyurethane foam material is fused withinthe flattened bead 51 to create a strong bond between the two materials.

Although the Figures herein show an oval-shaped composite laminatedstructure 54 having an oval-shaped pattern of depression 52 andflattened beads 51, it should be clear to one skilled in the art thatthe composite laminated structure 54 contemplated by the presentinvention attaches to any size, shape or form of a thermoplasticsubstrate having a laminate of polyurethane foam material or any othermaterial which has heretofore resisted bonding to such plasticsubstrates by conventional methods. It should also be clear that thenumber or arrangement of depressions 52 and flattened beads 51 can bevaried in accordance with the particular application.

The composite laminated structure 54 described above and illustrated inthe drawings is now available for a variety of applications. Thespecific application which prompted the present invention, that is,utilizing the fibers and pores of the polyurethane foam material toanchor to the polypropylene substrate a chemical composition such asdeodorant and/or anti-perspirant, exemplifies the type of applicationsbroadly contemplated by the present invention.

Thus, a relatively simple mechanical apparatus and method formanufacturing a composite laminated structure of polyurethane foam andpolypropylene has been described.

It is to be understood that the invention is not to be limited to thespecific construction or arrangement of the elements described hereinand shown in the drawings but that it is entirely within the spirit ofthe present invention to make modifications within the invention definedby the Claims.

What is claimed is:
 1. An apparatus for bonding a low density materialto a thermoplstic plastic substrate comprising,a. a base; b. a rotaryturntable rotatably connected to the base; c. at least one workpieceholder on the turntable to secure at least one thermoplastic plasticsubstrate to the turntable; d. a conductive heating assemblyincluding,i. at least one descendible and retractable welding iron forcontacting the plastic substrate, ii. a heating element for heating saidat least one welding iron to a predetermined temperature; and iii. meansfor actuating the descending movement of the at least one welding ironto melt the plastic substrate only at the points of contact; e. acompression assembly including at least one descendible and retractablecompression platen to emboss the low density material into the meltedareas of plastic; f. means for controlling the rotation of theturntable; and g. means for controlling the descending and retractingmovement of the at least one welding iron and at least one compressionplaten.
 2. The apparatus claimed in claim 1 wherein the at least onewelding iron is tapered and is circular in cross-section to facilitatethe forming of a raised circular bead of molten plastic at the point ofcontact.
 3. The apparatus claimed in claim 1 wherein the descending andretracting movement of the at least one welding iron and at least oneindividual compression platen and the movement of the work surface isaccomplished pneumatically.
 4. The apparatus claimed in claim 1 whereinthe means to control the descending and retracting movement of the atleast one welding iron and at least one individual compression platenand movement of the work surface, includes proximity switches whichsense the position of the at least one workpiece holder in relation tothe conductive heating assembly and the compression assembly.
 5. Theapparatus claimed in claim 4 wherein the rotary turntable is a circularindexing turntable having metal nibs fixed to its peripheral edge atpredetermined locations to activate the respective proximity switches.6. The apparatus claimed in claim 5 wherein timer relay coils areutilized to control the movement of the turntable, welding irons andcompression platens.
 7. The apparatus claimed in claim 1 wherein thereare eight individual welding irons in an oval-shaped pattern and eightindividual compression platens in a corresponding oval-shaped pattern.8. The apparatus claimed in claim 1 wherein the at least one weldingiron is made of aluminum.